This invention relates to improvements in electrosurgical instruments for coagulating and cutting biological tissue. In particular, the invention relates to an improved electrosurgical apparatus with limited current leakage for use with the said device.
Electrosurgical fulguration comprises the application of electric sparking to biological tissue, for example, human flesh or the tissue of internal organs, without significant cutting. The sparking is produced by bursts of radio-frequency electrical energy generated from an appropriate electrosurgical generator. Generally, fulguration is used to dehydrate, shrink, necrose or char the tissue, which operations are primarily to stop bleeding and oozing, or otherwise to seal the tissue. These operations are generically embraced by the term "Coagulation". Electrosurgical cutting comprises electric sparking to tissue with a cutting effect.
As used herein the term "electrosurgical pencil" is intended to mean an instrument comprising a handpiece to which is attached an electrode (the "active electrode"), which may be detachable or fixed. The pencil may be operated by a handswitch or a foot switch. The active electrode is an electrically conducting element which is usually elongated and may be in the form of a thin flat blade with a pointed or rounded distal end, or an elongated narrow cylindrical needle which may be solid or hollow with a flat, rounded, pointed or slanted distal end. Typically electrodes are known in the art as blade electrodes, loop or snare electrodes, needle electrodes and ball electrodes.
An electrosurgical pencil may be used for coagulation or cutting, or when the cutting is accompanied by hemostasis, by cutting and coagulation. The device of the present invention may be used to enhance both coagulation and cutting modes, as hereinafter described.
The handpiece of the pencil is connected to a suitable electrosurgical generator which generates the high frequency electrical energy necessary for the operation of the electrosurgical pencil. An electrosurgical generator suitable for use with electrosurgical electrodes and pencils is disclosed in U.S. Pat. No. 3,699,967, the disclosure of which is incorporated herein by reference. When an operation is performed on a patient with an electrosurgical pencil, electrical energy from the electrosurgical generator is conducted through the active electrode to the tissue at the site of the operation and then through the patient to a return electrode, placed at a convenient place on the patient's body, from whence it is returned via a patient pad or plate made of conductive material to the generator. A suitable circuit is illustrated schematically in U.S. Pat. No. 3,699,967.
The term "electrode" when used herein will generally refer to the active electrode.
The use of a stream of inert gas in conjunction with an electrosurgical electrode is known in the art. Thus, U.S. Pat. No. 4,060,088 (Morrison et al) discloses an electrosurgical method and apparatus for coagulating tissue by fulguration which involves establishing an electrical discharge in an inert gas by flowing said gas through a tubular electrode to which high-frequency electrical energy is applied.
U.S. Pat. No. 4,040,426 (Morrison) which is related to U.S. Pat. No. 4,060,088, discloses a method and apparatus wherein the inert gas flow is disposed adjacent the end of an active electrode to produce a primary electrical discharge in the gas and the apparatus includes a second electrode, electrically isolated from any source of biasing potential, which facilitates the establishment of an auxiliary electrical discharge from an electrostatic charge generated by the inert gas.
A third related U.S. Pat. No. 4,057,064 (Morrison et al) also discloses a method and apparatus for producing coagulation of tissue involving the use of a flow of inert gas and an active electrode.
The present invention provides improvements over the techniques disclosed in the above-mentioned Morrison patents, but since the basic concept of initiating an electrical discharge in an inert gas flow and the general circuitry for carrying out the procedure is a starting point for the apparatus and method of the present invention, the disclosure in each and all of the Morrison patents is incorporated herein by reference.
U.S. Pat. No. 4,781,175 discloses an electrosurgical technique for achieving coagulation involving conducting a predetermined ionizable gas not containing oxygen in a jet to tissue and conducting electrical radio-frequency energy in ionized conductible pathways in the gas jet.
Certain disadvantages present in commercially available units are overcome by the device and apparatus of the present invention.
Surprisingly, it has now been found that if at least one stream or jet of filtered inert gas is directed at a specific predetermined angle to impinge on the electrode of an electrosurgical pencil at or near the tip thereof in a device as hereinafter described the safety and efficiency of the pencil is enhanced. The pencil may be used both for cutting and coagulation, and can be made completely hand-operable; thereby increasing safety and flexibility.
U.S. patent application Ser. No. 07/494,249 describes and claims is a device for enhancing the safety and efficiency of a hand-operated electrosurgical pencil having an electrode with a distal end defining a tip for cutting or coagulating biological tissue, which device comprises a nose piece having a central axis and a hollow portion extending longitudinally about said axis, which hollow portion is adapted to accommodate said electrode, said nose piece containing conduit means defining at least one pathway for gas, which at least one pathway is disposed at an angle to said central axis so that gas passing therethrough impinges obliquely on said electrode at or near to the tip thereof and means for passing inert gas at a predetermined pressure and flow rate through said at least one pathway.
The configuration of the conduit means provides an angle between the gas pathway and the central axis of the nose piece within the range of about 5.degree. to 30.degree., preferably 12.degree., which corresponds to the angle at which the gas impinges on the electrode.
Preferably, the nose piece is part of a unit which is attached to the electrosurgical pencil. Thus, the unit may be made integral with the pencil or it may be made separately from the pencil so that the device of the invention may be used with an existing hand-switched or non-hand-switched electrosurgical pencil. The said nose piece is preferably slidably mounted on the unit, so that the point of impingement of the gas on the electrode may be adjusted as desired.
Since relatively high temperatures are generated at the tip of the electrode when performing an electrosurgical operation, the nose-piece preferably is made from a rigid high temperature resistant, electrically non-conducting material, for example a polysulfone or polycarbonate plastic.
The term hand-operated electrosurgical pencil as used herein is intended to mean an instrument which is operated by hand. Preferably, the switches which actuate or control the various functions, for example the coagulation mode or cutting mode, are hand switches located on the housing of the pencil itself and the general description herein relates to the preferred embodiment with hand switches. However, some functions may be controlled by foot switches or control mechanisms not located on the pencil itself and it is to be understood that embodiments using such alternative or additional controls are included within the generality of the term hand-operated electrosurgical pencil.
U.S. patent application Ser. No. 07/494,249 also describes and claims an electrosurgical apparatus for performing at least cutting or coagulation of biological tissue, which comprises, in combination, a hand-operated electrosurgical pencil comprising an electrode with a distal end defining a tip, means for supplying high-frequency, electrical energy from an electrosurgical generator through said electrode to said tissue and means for returning said electrical energy from said tissue to said generator to complete and electrical circuit, a controlled source of inert gas, a device attached to said electrosurgical pencil, which device comprises a nose piece having a central axis and a hollow portion extending longitudinally about said axis, which hollow portion accommodates said electrode, said nose piece containing conduit means defining at least one pathway for gas, which at least one pathway is disposed at an angle to said central axis so that gas passing therethrough impinges obliquely on said electrode at or near to the tip thereof, means for connecting said conduit means to said source of inert gas and passing filtered inert gas from said source at a predetermined pressure and flow rate through said at least one pathway.
The inert gas used in the device and apparatus of the above invention is a gas which is chemically inert and is not combustible in an electrical discharge nor will it support combustion. Preferred inert gases are the noble gases, i.e. helium, neon, argon, krypton and xenon. Particularly preferred for the purposes of the present invention is an inert gas selected from helium, argon, neon, and mixtures thereof. For some applications it is possible to use nitrogen, alone or in admixture with one or more of the noble gases.
In the operation of the device according to the above invention the filtered inert gas is used as a predetermined pressure and flow rate. The dimensions and configuration of the gas line and conduit means for conveying the gas are such that a preferred flow rate within the range of about 2 to 15 liters per minute (l/m) is provided by a pressure drop of approximately 1 to 13 p.s.i. This pressure drop is significantly lower than that used in existing devices and enhances the safety of the present above invention.
U.S. patent application Ser. No. 07/498,249 further describes and claims a method for performing an electrosurgical operation on biological tissue with enhanced safety and efficiency which comprises making the tissue part of an electrical circuit which is closed when said operation is performed, providing at least one stream of filtered inert gas, which at least one stream is directed at an angle to impinge obliquely on an electrode of a hand-operated electrosurgical pencil at or near to the tip of said electrode, bringing the tip of the electrode in close, non-touching proximity to or in contact with said tissue so that the said electrical circuit is closed by conducting electrical energy from an electrosurgical generator through said electrode and said tissue, and thereby performing the desired electrosurgical operation.
When the electrosurgical operations is coagulation, the method is performed by directing at least one converging stream of a filtered inert gas directly on to a tip of an electrosurgical electrode, bringing said tip in close proximity to the tissue, switching on the electrosurgical generator and choosing the coagulation mode for the electrode to initiate an electrical discharge in the inert gas and produce a spark between the tip and the tissue and maintaining the spark until the desired coagulation is complete.
A typical electrosurgical generator which is used with an electrosurgical pencil to perform the method of the above invention will generally provide electrical energy having a radio frequency of about 500 to 750 KHz. In the coagulation mode such an electrosurgical generator will provide an open circuit, peak to peak voltage within the range of about 1 to 10,000 V and a power output within the range of about 1 to 120 watts. If desired, the electrical circuit may include a step up transformer to increase the open circuit voltage available from the electrosurgical generator. Coagulation is preferably performed at a power output of from 20 to 120 watts. In the coagulation mode the voltage is generally sufficient to initiate an electrical discharge in the inert gas which manifests itself as a spark whose length varies according to the power of the RF electrical energy and the nature, pressure and flow rate of the inert gas. If desired, the apparatus also may include an electric booster for increasing the open circuit voltage to facilitate plasmatization of the inert gas at the onset of the coagulation mode.
When the electrosurgical operation is cutting, the method is performed by directing at least one converging stream of a filtered inert gas on to an electrosurgical electrode to impinge obliquely on said electrode at a predetermined point adjacent to but away from the tip thereof, switching on the electrosurgical generator and choosing the cut mode for the electrode, placing the tip of the electrode in contact with the tissue and drawing it across the tissue to produce the desired cutting operation.
In the cutting mode, an electrosurgical generator such as that described above will provide an open circuit, peak to peak voltage of about 1 to 6,000 Volts and a power output within the range of about 1 to 300 Watts. Cutting is preferably performed at a power output of from 30 to 150 Watts.
In the cutting mode, the open circuit voltage is generally not high enough to continuously plasmatize the inert gas and initiate and maintain an electrical discharge. Accordingly, unlike coagulation, where the operation is enhanced by the initiation of an electrical discharge, the function of the inert gas is to provide a shroud around the cutting electrode. The resulting advantages include dispersion of combustible gases around the site of the operation; reduction in the amount of eschar or charring of the tissue; blowing away gases and vapors, including smoke generated in the operation, thereby providing better visibility for the surgeon; and enhanced hemostasis.